1. Field of the Invention
The present invention relates to a metallic glass component with its surface layer having both chromatic color properties and durability of a film such as corrosion resistance, weathering resistance, fingerprint wiping properties, and peeling resistance, and a method for forming the surface layer.
2. Description of the Related Art
Metal glass has a composition in which an amorphous metal is formed even at a cooling temperature of not higher than 100 K/second, and there is known a method for forming a large-shaped amorphous metal (bulk metallic glass) directly from a molten metal by using already developed water hardening, arc melting, mold casting, high-pressure projection molding, suction casting, or some other methods. Metal glass has a unique mechanical characteristic of being free from a defect as having high strength, a low Young's modulus, high corrosion resistance, and a grain boundary, which is an essential property of an amorphous metal and is not of a crystalline metal. Furthermore, it has been possible to obtain a large-sized amorphous bulk body by the above-mentioned methods, and it has been widely expected to put the bulk body into practical use.
The surface of such metallic glass is treated so as to have an added value as a component in addition to its essential, excellent mechanical characteristics and physical properties. For example, (1) anodization (e.g. Patent Document 1) and (2) atmosphere heating oxidation (e.g. Patent Document 2) have been attempted as conventional surface treatment, and the surface has been colored by such treatment.    Patent Document 1: National Publication of International Patent Application No. 2005-509090 “Improved metal frame for electronic device and flat panel display”, Liquid metal Technologies    Patent Document 2: Japanese Patent Laid-Open No. 2003-166044 “Method for toning zirconium-base amorphous metal”, YKK Corporation
However, (1) although anodization enables vivid coloring depending upon conditions, since it is treated with an electrochemical function, coloring has often been nonuniformly finished in the case of three-dimensionally treating a large area of the surface of a metallic glass component. Further, for the same reason, a tone of color has sometimes been changed over time despite the passivated surface.
Moreover, (2) atmosphere heating oxidation not only leads to coloring with limited chromatic colors, but also, coloring has often been nonuniformly finished in the case of three-dimensionally treating a large area of the surface of a metallic glass component. Further, there has been a drawback in that, on an oxide film formed by atmosphere heating, natural oxidation proceeds over time to bring about a change in tone of color.
Furthermore, there has also been problems in that, on a nonuniform film formed by above (1) anodization or (2) atmosphere heating oxidation, a corrosion product tends to be generated from salt or mineral floating in the air, a mineral element contained in sweat or a fingerprint when the film is touched with a hand, or the like, to bring about deterioration in appearance and durability.